If you're looking for manga similar to De Sport Fighter Z, you might like these titles.
Famicom Rocky is basically Rocky the movie, but with old NES-era video games. The series stars an ineloquent brute of a protagonist who has long, extensive training montages so that he can dramatically compete against vaguely imposing rivals who, for narrative purposes, are deluded into thinking they're better at video games than him.
The Spin off takes place in a very different setting, where instead of the Mafia, Racers exist. Racers use go-karts, and during a race anything goes, including any type of interference to prevent your opponent from winning. Tsuna is the descendant of the person know as the greatest racer in history, Primo but is absolutely horrible in the sport himself and has lost 999 races in a row. Tsuna races for Team Vongola, and is known as the disgrace of Nammimori town.
Two boys who would never have been able to meet each other under normal circumstances will now carve their mark in boxing history!